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Monday, August 02, 2004

Rover Update: Wintering on the Red Planet


That double-header of a rover mission to Mars -- Spirit and Opportunity -- are both moving toward fresh rounds of science-gathering and could survive far longer than once expected.
Opportunity at Meridiani Planum, has received the go-ahead to "deep dive" into a large impact crater dubbed "Endurance", while on the other side of Mars, the Spirit rover at Gusev Crater is within days of reaching the "Columbia Hills" and studying geology that appears to offer unique insight into that region’s history.
Meanwhile, scientists and engineers that operate the robotic twosome are looking at "wintering over" schemes -- putting the mechanized explorers in hibernation mode, and then restarting their duties on Mars next spring.
Mars rover scientists detailed future plans at last week’s American Astronomical Society (AAS) meeting, held in Denver, Colorado.
Taste-testing the hills
"Things are about to get very, very interesting," said Steve Squyres of Cornell University in Ithaca, New York, and principal investigator for the science payload carried on each of the Mars rovers.
At Gusev Crater, Spirit has been making remarkable progress driving toward the Columbia Hills. "The hills are starting to get too big. So the images cut off the top of the hills…and that’s kinda cool," Squyres said. Those pictures of the hills already reveal exposed bedrock and other features that look "very interesting, indeed," he added.
"We should pull up at the base of those hills within another week, or a little bit more. Then we’ll see what we see," Squyres said.
A preliminary plan is to have Spirit traverse southward, along the margin between the hills and the plains of Gusev Crater. A variety of geological features is in that direction. "I don’t have high confidence to be able to climb high into the hills," Squyres said. "But as we get closer and closer…I can see that plan being altered significantly."
Squyres told the AAS audience that Spirit will first "take a taste" of the hills with its science gear, "then hang a right". Exactly what the traverse will be like after that will be decided by what is found, he said.
"That’s what is interesting about this mission. You can’t plan too far ahead because Mars will surprise you," Squyres explained.
Enduring Endurance
The Opportunity rover at Meridiani Planum is perched at the edge of the stadium-sized Endurance impact crater -- a feature roughly 65-feet (20 meters) deep and brimming with thick and old layers of bedrock and rich in sulfates, hematite, and basalts.
Careful study has been done of a section of Endurance tagged "Karatepe" -- a layered band of rock. That piece of real estate is seen by rover drivers at the Jet Propulsion Laboratory (JPL) in Pasadena, California as a safe entrance ramp into the roughly 430-feet (130-meter) diameter crater. This spot is less steep and more approachable than the rest of the crater’s rocky outcrops.
"It is a rocky surface, but there are these little spherules we call blueberries all over the place," said Jim Bell of Cornell University and leader of the panoramic camera team for the Mars Exploration Rovers.
Bell told SPACE.com that the potential risk of having Opportunity drive on a plywood-like surface covered with spherules acting like ball-bearings has undergone detailed assessment. "The slopes are gentle enough. The rover wouldn’t go tumbling down the hill…but it would slide and be hard to control. You could get in a situation where you sit spinning your wheels trying to get back up," he said.
Big cliffs
Squyres said Endurance crater is "just a stunning, beautiful, spectacular place." But such a hole in the ground "can be a permanent rover trap," he added, and "a one-way trip doesn’t appeal to any of us very much."
"This is a dangerous place for a rover. There are big cliffs that we could drive off and die. So we’ve been very careful here," Squyres said.
In going into the crater, and taking a prudent route, Squyres said that Opportunity would drive slowly forward with its robot arm stretched out, steer to a band of exposed rock, do its business and then back out, straight up the hill.
"The vehicle goes backwards as well as it goes forward," Squyres pointed out.
So far, so good
Regarding the overall health of the twin vessels of Mars exploration, both robots continue to perform well.
Several things could kill the rovers, such as a key electronic part failure or the wearing down of a critical mechanical piece of equipment. To date it has been so far, so good as the robots continue to march their way across the martian landscape.
"If both of those things hold out, then what is probably going to get us is dust build-up on the solar arrays," Squyres said. "Right now, we’re seeing a pretty sharp drop off in solar power on both vehicles. That’s a consequence of both the onset of winter and declining solar power because of the dust build-up."
Despite this issue, Squyres said rover engineers think the two robots will survive through the winter and to the next spring on Mars.
Wintering over: spring back to life?
Staying alive is tougher for Spirit than it is for Opportunity. That’s due to Spirit’s higher latitude exploration zone on the red planet, Squyres reported. "We’re already looking at maps of the Columbia Hills and trying to pick a good spot to winter over," he said.
Part of the wintering over strategy will involve positioning the rovers to soak up as much continuous sunlight, even as the Sun moves low in the martian sky, Bell said. Secondly, the robots are to be oriented so that communications links with orbiters zipping overhead is maximized, he pointed out.
"It’s a combination of those two things -- finding that sweet spot," Bell said.
Coming out of hibernation mode in the spring, "we’re looking at the final demise of these vehicles perhaps as late as the onset of our second winter on Mars," Squyres concluded



















Natural Sunblock: Sun Dims in Strange Ways


When Venus crossed the Sun June 8, showing up as a clear black dot to the delight of millions of skywatchers around the world, astronomers noted something less obvious: The amount of sunlight reaching Earth dipped by 0.1 percent for a few hours.
The result was not a surprise, but since Venus hadn't transited the Sun in more than a century, the effect had never been measured.
The drop in sunlight was similar to what happens when a large sunspot crosses the solar surface. But these forms of natural sunblock don't behave as you might expect, as witnessed by folks who froze their tails off a few hundred years ago across much of the Northern Hemisphere.
Two types of transits
Sunspots are cool, dimmer regions of the solar surface, packed with pent-up magnetic energy that sometimes unleash storms of X-rays and superheated gas. When they transit the face of the Sun, they are often visible without magnification to skywatchers using safe viewing techniques (looking directly at the Sun can cause permanent eye damage).
The planets Venus and Mercury, both orbiting inside Earth's path, also transit the Sun.
Sunlight reaching Earth is monitored by NASA's Solar Radiation and Climate Experiment (SORCE) satellite. The Venus transit proved to be a good test of instrument sensitivity.
"Because of its distance from Earth, Venus appeared to be about the size of a sunspot" on June 8, said Gary Rottman, SORCE Principal Investigator and a scientist at the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder.
Rottman and colleagues saw greater reductions in the Sun's energy coming Earthward during a stretch of intense solar activity last October, when several huge sunspots generated a record-breaking string of solar flares. At one point, sunlight dimmed 0.3 percent for about four days, due mostly to three large sunspot groups.
"This is an unprecedented large decrease in the amount of sunlight," Rottman said, and it is comparable to the decrease that scientists estimate occurred from roughly 1645 to 1715. During a broader period, from the 1400s to the 1700s, Europe and North America were plunged into what came to be called the Little Ice Age.
Dearth of sunspots
Scientists could not measure solar radiation back then. But sunspots were recorded by several astronomers, and Rottman and others believe there is a correlation between the climate of the time and the lack of sunspots.
"For a period of about 50 years, there were almost no sunspots," Rottman said in a telephone interview. "The total amount of radiation was, we assume, about three-tenths of 1 percent less" than in normal periods of solar activity.
If you've been paying attention, that might sound backward. Rottman's team measured a decrease in sunlight when Venus transited the Sun, and similar decreases are recorded when sunspots are present.
So why would there have been less radiation in the late 1600s when there were very few sunspots? Rottman explains:
Sunspots indicate greater solar activity in general. While they do dampen sunlight while on the face of the Sun, they are surrounded by intensely bright regions called "faculae" or "plage." When sunspots are on the limb of the Sun -- just rotating onto or off of the face -- the plage are prominent from our vantagepoint, creating a significant increase in radiation that far outweighs the dip of radiation caused by the rest of the sunspot's transit.
Seen on a graph, total visible and infrared radiation increases just before a sunspot appears, dips slightly for several days as it crosses the surface, then increases again as it disappears.
A lack of sunspots indicates inactivity in the Sun, and less radiation overall.
Still a mystery
The reduced solar activity of the 1600s and 1700s is called the Maunder minimum, after the solar astronomer Edward Walter Maunder, who during the 1800s investigated the historical sunspot records.
Nobody knows for sure why it occurred or whether it will happen again anytime soon. In fact, the whole concept remains controversial, because it's not clear how well astronomers were counting sunspots during the Maunder minimum. And the exact tie to climate is not understood. Most tend to agree, however, that there was a distinct lack of solar activity.
"Something very different was happening during the 17th Century, and it produced a much more permanent change in the Sun's energy output at that time," Rottman said.
Live Sun Cam
Mysteries of the Sun
The Sunspots of October 2003
Photos of Venus Crossing the Sun

an astronomy Communities in orkut

my frinds (me) Communities in orkut
description:this group want to tell you the latest news of astronomy all around the world
category:Science & History
owner:Mohammad Kazemi
type:public
forum:anonymous
language:English
location:Iran
created:Wednesday, July 28, 2004

an astronomy gruop

AACI
This club was established for all Iranian Amateur astronomers to disccuss about all subjects in astronomy and astronomy news .
All members can send their astronomy news to others by sending to this E-Mail address : aaci@yahoogroups.com

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Clear skies

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The Atom

........................The Atom..................{part one}
Most of us are familiar with the fact that any matter whether a liquid, or a solid, or a gas, is made up f molecules. A molecule is the smallest particle that a compound can be reduced to before it breaks down into its element. For example, if we took a grain of table salt and kept breaking it in half until it got as small as it possibly could and yet still be salt, we would have a molecule of salt. If we then broke it in half again, the salt would change into its elements.

1-a grain of salt
2-can be reduced to
3-a molecule of salt {sodium chlorine: . .}
by mohammadreza_naserian

A ISACK ASIMOF WRITING: I, Robot

As scenes of rioting robots are in the trailer, it is probably not giving away too much to say that there are elements of I, ROBOT that resemble another 20th Century Fox science-fiction film of long ago, namely CONQUEST OF THE PLANET OF THE APES. Now, robots and apes are not all that similar, but both movies concern near-future societies in which a non-human slave force shows signs of rebelling against the ruling class. Nobody will be surprised that I, ROBOT is infinitely superior in terms of special effects and it’s got much better plotting – the screenplay by Jeff Vintar and Akiva Goldsman, from Vintar’s story, which in turn derives the basic precepts of its universe from the work of Isaac Asimov, is in fact quite a good murder mystery. What APES has that I, ROBOT lacks is a passionately subversive spirit. This may seem like an irrelevant criticism, as good science-fiction (especially in the movies) need not be in the least subversive to work. However, I, ROBOT is just out there enough that we can feel something a lot more outrageous pulsing along under the more than proficient but less than daring surface.
In 2035, most menial work is done by polite, intelligent-seeming machines that resemble contemporary crash test dummies. Robot-hating Chicago homicide detective Del Spooner (Will Smith), newly back at work after a nightmare-inducing tragedy, is called in to investigate an apparent suicide at U.S. Robotics. The victim is the firm’s chief scientist, Dr. Alfred Lanning (James Cromwell), who had met Spooner in the past and has for some reason left a holographic message for the detective. Spooner suspects murder – in fact, he believes Lanning was killed by a robot. This would seem to be impossible, as the first and most important of the Three Laws of Robotics states that a robot cannot harm a human, or through inaction allow a human to come to harm. However, a prototype robot called Sonny (voiced by Alan Tudyk) appears to be able to violate the Laws of Robotics and also (much to Spooner’s consternation and dismay) seems capable of independent thought and even emotion. But why would this robot kill the creator he claims to love? And what is U.S. Robotics chief Lawrence Robertson (Bruce Greenwood) trying to hide?
The puzzle aspect of I, ROBOT is its most compelling feature. The structure is strong and we genuinely do not guess exactly what is going on right away, although the clues are laid out for us fairly. Another bonus is Smith’s performance, which is intelligent and charismatic enough to carry us along even over the rough patches. Smith’s demeanor is noticeably darker here than usual – he’s not a cold fish and he’s definitely got a sense of humor, but the rage under the surface is a lot closer to volcanic than playful this time out. As the voice and basis for the expressive if very subtly detailed face and form of Sonny, Tudyk is thoughtful and appealing, making the self-aware robot the most likable character in the film
Here is where the movie runs into one of its problems. Several key supporting performers have apparently been directed to be cold and unemotional – the energy level goes way down during their scenes, some of which entail massive exposition that could have used any and all available torque. Also, while this may be a controversial view, the gleaming, basic look of the robots is visually intriguing at first, but comes to look uninflected later – the CGI when the robots are not interacting with live performers is dimensional yet feels more digital than visceral.
Director Alex Proyas stages some great action sequences and he and the writers show signs of having a message they would like to convey (there are a couple of plot points that are analogous to contemporary political issues). They also want to put across some thought-provoking moral ambiguity, which is usually welcome in movies, especially in this genre. However, they tend to pull their punches a bit, so that the ending feels both diffuse and defused. They want us to root for both humanity in general (even when we see humans bullying the subservient robots) and for Sonny’s right to exist in specific terms (although it is plain that most if not all of his brethren really are high-functioning automatons). In terms of statement, they have their cake and eat it, too – it just tastes a bit bland that way.

The Future of Travel: Aquatic to Cosmic Destinations

Future travelers will be putting down their luggage in far-flung places, underwater, in the air and around the planet. They'll get amazing views from bizarre living quarters that build on "outrageously successful" billion-dollar projects on Earth, and they'll take adventures that have long been the province of science fiction.
That’s the vacationing landscape of the 21st Century envisioned by various travel analysts.
Thomson Holidays, a leading travel and destination group based in the United Kingdom, just issued a report on the future of leisure travel. The report is an outgrowth of the Future Holiday Forum, an event Thomson organized late last year to bring together architects, technologists, travel journalists, experts on social trends of the future, as well as authorities on sustainable tourism.
The conclusions are a sweeping preview of the changing needs and expectations of globetrotting travelers two decades out.
They include way-out expeditions and down-to-Earth jaunts. No-frills travel will include brief, affordable breaks to locations such as Moscow, Rio and Cape Town. The Middle East and South America will vie for top billing with traditional European destinations.
And others say regular civilian flights to space could finally become reality.
Ride the Cosmoplane
Development by 2024 of the Cosmoplane - a successor to Concorde - will make it possible for adventurous travelers to go farther and faster. More traditional types of destinations won't be crowded out of the picture. In fact they'll just get more crowded as an aging population swells the ranks of folks with time and money to spare, looking for new places to wander.
China is predicted to be the world's number one tourist destination within 20 years. Elsewhere in Asia, countries along the Silk Road such as Kyrgyzstan and Turkmenistan are likely to see a dramatic rise in tourist numbers as backpackers seek out new destinations.
Other destinations that can expect throngs include Qatar in the Middle East with its positioning as the 'Real Arabian Experience', Ljubljana in Slovenia as a city break, and Slovakia for its natural scenery and outdoor sports potential.
Then there’s Brazil for its unbeatable combination of beaches, rainforest, nightlife and cities, according to the report.
Other key predictions:
In the 2020s, people over 50 will outnumber younger generations. This aging but very active population will holiday more frequently in increasingly exotic locations, thinking nothing of jetting off to destinations all over the world.
The 'real holiday' experience for travelers is seeking many different experiences. That includes "zorbing," in which "zorbonauts" climb inside a large inflatable ball and are rolled downhill; skydiving; watching polar bears in the wild; and mind-and-body getaways at yoga retreats.
A new breed of tourist will seek out eco-friendly holidays. Less than 1 percent of people currently look for sustainable destinations, but this is predicted to grow to 5 percent by 2024, with many people only traveling to places that protect or benefit the environment.
Beyond Earth
In the wake of the first private, manned mission to space -- SpaceShipOne's history-making trip beyond the atmosphere on Monday -- space hotels may also be on the horizon, according to other analysts.
"It's only a question of time and money," explained Howard Wolff, senior vice president of the international architecture and design firm Wimberly Allison Tong & Goo (WATG), from his office in Honolulu, Hawaii.
Wolff noted that the ability to create habitats in space exists.
"The obstacle is not technology," he told SPACE.com. "The Catch-22 is that a space hotel won't be affordable until there is a mass market for space tourism … and there won't be a mass market until it's affordable."
The missing ingredient, Wolff said, is a commercially viable fleet of reusable launch vehicles. "You can't have a successful hotel if you don't have the means of getting people there."
Visionary clients
Wolff, who is spearheading his company's development of concepts for a hotel in Earth orbit, is optimistic.
"The interest exists among prospective travelers," he said. "Several companies are already testing the next generation of vehicles. The hotel investment community is intrigued but skeptical. All it will take is one entrepreneur with deep pockets who is willing to take a bit of a financial risk."
WATG has been involved in ambitious on-Earth destinations for travelers in 130 countries on six continents, such as: The Venetian in Las Vegas; Atlantis, Paradise Island, in the Bahamas; and The Palace of the Lost City in South Africa.
"We've worked with visionary clients who have invested well over a billion dollars to create a single resort that generates a handsome return on investment," says Wolff. "Others thought they were crazy, but their properties turned out to be outrageously successful."
Wolff predicted that the first hotel in space will be a mixed-use project with commercial and research applications that will make it easier to finance.
What will fly?
WATG’s visionary space hotel concept includes portions that will have partial Earth gravity "for creature comforts like being able to flush a toilet and take a shower" as well as weightless environments "for scientific experiments as well as the sheer thrill of the experience," Wolff explained.
Having designed destinations for well-heeled travelers for over half a century, the folks at WATG have a pretty good handle on "what will fly," a confident Wolff added.
Fly indeed. For those among us who want to stick closer to Earth, the WATG futurists also envision a potentially revolutionary helium-filled airship hotel.
The concept melds elements of traveling by cruise ship, hot air balloon and airplane. No need for travelers to unpack. Passengers can hit any number of destinations in a given trip. Unlike an airplane, the airship hotel would cruise at a leisurely pace and at low altitude, giving camera-snapping sightseers picturesque viewing along the travel route.
Deep Six those anxieties
Afraid of the heights, be it spinning around in a space hotel or taking cloud-banking turns in an airship?
Then deep six those anxieties and check into Hydropolis.
Planning is already underway for this watery habitat to be built in Dubai, the second largest of the seven emirates that make up the United Arab Emirates.
Dubai is being tagged more and more as the Las Vegas of the Middle East, known for its over-the-top hotels. Hydropolis is no exception, albeit under the water. It is slated to open in December 2006.
Planning documents for the venture point out a few factoids: For one, the medium "water" is a basic elixir of life. Then there’s the basic fact that a human is 75 percent of water, and that a person’s wellbeing requires regeneration of this basic substance.
"Sanus per aquam" -- health through water -- is therefore not a trend, "but rather an expression of health-consciousness, a synonym for well-feeling, and of harmony of body, mind, and spirit," Hydropolis designers suggest.
Hydropolis is to be located off the Jumeirah coast. As the world's first underwater luxury hotel, the plan is to construct three distinct areas: one on land, a connecting tunnel, and the submarine complex. There will also be a ballroom, spa, restaurants, shops and separate underwater villas.
"Hydropolis is a splendid refuge far away from the stress factors of everyday business life and is ideally suited for guests from top management seeking to regenerate their inner strength," explains a project fact sheet.
Pod hotels
Hotel "pods" that can be moved to any spot on the globe is the way to go, contends Nadi Jahangiri, Director of m3architects in London. He and collaborator Ken Hutt foresee the pop-up pods planted anywhere from the Australian rainforest to the Antarctic.
"We propose a temporary, licensed, pre-fabricated, self-sustaining, transportable facility that can be located on sites and locations all over the planet in places where establishing a traditional holiday resort would be unacceptable environmentally and politically," Jahangiri and Hutt reported at the Future Holiday Forum.
These futuristic pods can remain in place for up to 15 years, or could be dismantled as demand drops for a destination. Constructed on stilts, the holiday pod is designed to leave only a small mark on the local environment.
A pod would be fabricated off-site, then transported to a select location and assembled on the spot.
Each pod would be self-sustaining and easily transportable from site to site. All waste produced by the hotel pod would go into a disposal unit at the base of the structure. The hotel would create its own operating power, making use of Sun-soaking, energy-providing photovoltaic cells.
Different sized rooms within a hotel pod can be upgraded or downgraded according to a tourist’s travel budget. Inside the rooms, ‘active’ walls and floors will show changeable images. Pod guests can use this mode-changing select-switch and pick whatever mood they wish, be it an ocean panorama, desert landscape, or jungle scene.
Guests would arrive by helicopter.
Hugh Edwards, Marketing Director for Thomson, said the Future Holiday Forum -- which focused on Earth-bound travel -- underscored a number of trends. While he expects destinations such as Spain, Greece and Italy to remain popular, the forecasts are based on projections from experts who have carried out in-depth research into future trends.
"Holidays in pods, mini-breaks to Rio and family holidays in Qatar are very likely scenarios for holidays of the future," Edwards said.
MORE : WWW.SPACE.COM

Moon To Provide a Stepping Stone to Mars and Beyond

By: Brian BergerSpace News Staff Writer
Thirty-five years after the world watched three Americans leave Earth on a mission to be the first to land on the moon, the United States is plotting a return to the lunar landscape. But while the destination is the same, the motives have changed.
Then the goal was to prove to a divided world simply that it could be done and done best by a free society. Now the driving motivation is to demonstrate the technologies and hone the skills needed to venture beyond Earth’s own backyard.
U.S. President George W. Bush, in dropping the exploration gauntlet during his speech at NASA headquarters in January, said the United States would return to the moon by 2020 “as a launching point for missions beyond.”
Beginning no later than 2008, Bush said, the United States would begin launching robotic missions to the moon to prepare the way for extended human lunar expeditions.
Bush said the moon is a good place to test the equipment and approaches needed if humans are to operate in even more challenging space environments. And the moon’s natural resources and other attributes, he said, have the potential to reduce the costs of further space exploration.
Paul Spudis, a planetary scientist and a member of the presidential commission advising Bush on implementing a national space exploration strategy, said the president got it right when he called for going to the moon first.
“We are going to the moon to basically take the first step beyond low Earth orbit,” Spudis said. “The key thing the president articulated in the vision is the use of lunar resources. It’s something we don’t know how to do, but something we need to be able to do if there is to be a big future for humans in space.”
Doug Cooke, NASA’s deputy associate administrator for exploration systems, said the U.S. space agency’s moon agenda is still very much a work in progress.
“At one end of the scale, we are talking primarily about preparation for exploration beyond the moon -- developing vehicles, spacesuits and other hardware and testing operational capabilities and techniques,” Cooke said. “At the other end of the scale, if there are outside interests that want to develop the moon and they come into play, that could drive us harder toward more permanent capabilities.”
Cooke said NASA is hard at work evaluating a range of approaches to accomplishing the broad objectives spelled out by the president. NASA has put out a broad call to industry for long range lunar mission proposals and hopes to award several study contracts before the end of the year. Cooke said NASA should have a better understanding of the range of possible approaches by September.
Some moon advocates, such as Spudis and Klaus Heiss, director of High Frontier, favor picking a promising plot of lunar real estate and plopping down as much infrastructure as needed to sustain a variety of human and robotic activities. Others, such as Marc Cohen, a researcher at NASA’s Ames Research Center, are advocating building a mobile habitat that can traverse the lunar surface to new destinations while waiting for its human occupants to arrive.
Regardless of how NASA gets there, Cooke said the driving motivation behind going back to the moon is to prepare for increasingly challenging missions.
“We’ve always thought the moon was important, at the very least, for preparing future exploration,” he said. “It has been 35 years since we did it for the first time and a lot of the experience we gained during the Apollo program has been lost.”
As NASA sets out to design the vehicles, habitats and other equipment it will need for extended stays on the moon, Cook said the agency also would be keeping one eye on Mars. “We need to be mindful of the long range of exploration,” he said. “The more that we can do that is common for what we will need for Mars missions, the more efficiently we can progress down that path of exploration.”
Perhaps the most tantalizing feature the moon and Mars have in common is the presence of water -- a critical element for sustaining a human presence, and not just for drinking. Cooke sees water, whether present in the surface or atmosphere of Mars or frozen in the lunar surface, as a valuable source of fuel for all manner of space vehicles.
“The water ice is probably the first thing that would be investigated because it might have immediate application to various missions,” Cooke said.
Those applications, Cooke said, include providing potable water, breathable oxygen and fuel for nuclear thermal or chemical rockets.
The search for water could well lead to the lunar poles, a destination favored by Spudis and others in large part because of the intriguing signatures returned by the Lunar Prospector and Clementine missions of the early 1990s.
“You can readily make the case that because of the presence of [potential resources] in the dark areas and near permanent sunlight offers an ideal environment to learn the things we need to learn,” Spudis said.
BY : WWW.SPACE.COM

NASA's Lunar Reconnaissance Orbiter Mission Takes Shape

NASA engineers are hard at work on a lunar spacecraft expected to be the first in a wave of robotic probes that will pave the way for future human missions.
The spacecraft, called the Lunar Reconnaissance Orbiter (LRO), is the first mission out of the gate under NASA’s space vision of sending more robot and human explorers beyond Earth orbit.
“This mission is the first concrete step in laying the groundwork for humans to go back to the moon,” said Jim Garvin, the lead scientist for moon and Mars exploration at NASA headquarters in Washington. “So there’s a lot resting on its shoulders.”
Set for a 2008 launch, the probe is expected to circle the moon for at least one year and return detailed maps of the lunar surface, data on the moon’s radiation levels and an in-depth look at its polar regions for resources that could be tapped by future astronauts.
But everything is still on paper, and project engineers have a narrow window in which to design, build and integrate the spacecraft to meet their intended launch date.
Engineers at NASA’s Goddard Space Flight Center in Greenbelt, Md., are designing the actual spacecraft bus, while the instrument payload will be provided by private industry. An Acquisition of Opportunity for the payload was announced June 18 and a final design is expected to be in hand in November.
“This is certainly a quick development mission,” Garvin said in a telephone interview. “There’s not a lot of time to generate a high-reliability flight mission.”
Exactly how LRO will make its moon measurements is still an unknown, though mission planners can envision a number of routes private payload designers might take.
“This is not a science mission, it’s a measurement mission,” Garvin said. “For example, we don’t have any lunar maps at the scale of a landing site since the Apollo missions, but there are a variety of ways to make them.”
LRO’s topographic map-making instruments may include one or more of the following: conventional radar, laser-based range systems like Light Detection and Ranging, or a system known as synthetic aperture radar that combines radar measurements with computer analysis to make detailed measurements.
High-resolution cameras similar to those used in the one-meter resolution Ikonos satellites owned by Space Imaging Inc. will be required to photograph the lunar surface. Part of LRO’s mission is to identify potential landing sites for future missions and any nearby hazards, such as boulders, which could shift and knock a lander or human down, Garvin said.
LRO’s imaging system also is expected to be able to look into permanently shadowed regions of the moon and its polar regions to look for signs of large water ice deposits — on the scale of football fields — that could be viable resources in future missions.
A critical part of any prolonged human stay on the moon is the amount of radiation astronauts will be subject to during a mission. LRO’s instrument set also should be able to determine the biological effects of that lunar radiation environment.
Jim Watzin, lunar exploration program manager at NASA’s Goddard Spaceflight Center, said NASA engineers have already begun preliminary design work on the spacecraft.
Even without a final payload in hand, Goddard engineers have been able to define some of the parameters their spacecraft must meet.
Since time is of the essence, LRO will make use of conventional technology instead of untested tools. That means a chemical-fueled rocket will push the spacecraft moonward as opposed to more exotic approaches, such as an ion engine or other propulsion methods.
A conventional approach also keeps costs down, an important point since the mission’s total budget from development through first-year operations is set at about $90 million.
“We’re constrained to be a Discovery class [mission] in cost, so we have to limit ourselves to a Delta 2 launch vehicle,” Watzin said.
Because of that rocket limitation, project engineers know their final spacecraft must weigh about 1,000 kilograms (2,200 pounds), half of which will be propellant to not only push LRO to the moon, but keep it in the proper lunar orbit once it arrives, Watzin said. And because the spacecraft will be making detailed maps from an altitude of about 50 kilometers (31 miles), LRO will need to be able to accurately point itself in any direction, he added.
The spacecraft will also require a robust power and communications system to relay large amounts of data to Earth and sustain its science instruments.
“We’re pushing the spacecraft design as far as we can go knowing, in general, what the capabilities it needs and having some idea on the classes of instruments it will have,” LRO project manager Craig Tooley said in a telephone interview.
Lunar pathfinder
The future of NASA’s lunar exploration exploits may ride heavily on the data LRO sends back to Earth.
If LRO’s lunar maps point out an obvious point of interest on the surface, the space agency may choose a robot lander mission to drop on the area for a more detailed study. A second possibility would be a second orbiter, armed with more science instruments, to conduct more reconnaissance.
“The early months of [LRO] would target things that the second mission would follow in this lunar robotic program,” Garvin said. “But we’re talking about moderate-class missions here, not billion-dollar, 100-yard wandering rovers.”
www.space.com

The 2004 Perseid Meteor Shower

Meteoroids in space since the Civil War will spice up this summer's Perseid meteor shower

The annual Perseid meteor shower is coming, and forecasters say it could be unusually good.
The shower begins, gently, in mid-July when Earth enters the outskirts of a cloud of debris from Comet Swift-Tuttle. Dust-sized meteoroids hitting the atmosphere will streak across the night sky, at first only a sprinkling, just a few each night, but the rate will build.

By August 12th when the shower peaks, sky watchers can expect to see dozens, possibly even hundreds, of meteors per hour.
Right: Photographer Nathalie Dautel caught this Perseid streaking through the Milky Way in 2001. [More]
This is a good year for Perseids, for two reasons, explains Bill Cooke of the NASA Marshall Space Flight Center. First, the Moon is new in mid-August; moonlight won't spoil the show. Second, in addition to the usual shower on August 12th, there might be an extra surge of meteors on August 11th caused by a filament of dust newly drifting across Earth's orbit.
The filament, like all the rest of the dust in the Perseid cloud, comes from Comet Swift-Tuttle. The difference is, the filament is relatively young. It boiled off the comet during the Civil War, in 1862. Other dust in the cloud is older (perhaps thousands of years old), more dispersed, and responsible for the month-long shower that peaks on August 12th. The filament will eventually disperse, too, but for now it retains some of its original ribbon-shape.
If predictions are correct, Earth will plow through the filament on Wednesday, August 11th at 2100 UT (5 p.m. EDT). This will produce a surge of mostly-faint meteors over Europe and Asia. Observers might see "as many as 200 meteors per hour," says Cooke, who recommends getting away from city lights to watch the flurry.
(Note: Perseids favor northern latitudes. Because of the way Comet Swift-Tuttle's orbit is tilted, its dust falls on Earth's northern hemisphere. Meteors stream out of the constellation Perseus, which is barely visible south of the equator.)
Later that night, observers in North America can see the "traditional Perseid peak" caused by the older dust from Swift-Tuttle. "Expect 40 to 60 meteors per hour, some of them bright," says Cooke.
The best time to look for these "traditional Perseids" is during the hours before dawn on Thursday, August 12th. Set your alarm for 2 o'clock in the morning; go outside; lie down on a sleeping bag with your toes pointed northeast. You'll soon see meteors racing along the Milky Way.

Above: The pre-dawn sky on Aug. 12th. The Perseid radiant is denoted by a red dot. While you're looking for meteors, check out Venus and the crescent Moon, too, near the horizon.
Can't wake up at 2 a.m.?
Try looking around 9 or 10 p.m. on Wednesday, Aug. 11th when Perseus is hanging low in the eastern sky. You won't see many meteors then, but the ones you do see could be memorable. Shooting stars that emerge from the horizon and streak horizontally through the atmosphere are called "Earthgrazers." Slow and colorful Earthgrazers are a good target for city dwellers, because they are so bright.
Dust from Comet Swift-Tuttle hits Earth. What about the comet itself?

Americans Lewis Swift and Horace Tuttle, working independently, discovered the comet in 1862, and they watched the Aug. 11th filament billow into space. Three years later Giovanni Schiaparelli (of Martian "canali" fame) realized it was the source of the Perseid meteors. He understood that the comet could come close to Earth, but in those days no one worried about such things.
Right: 19th century astronomer Giovanni Schiaparelli. [More]
The idea that comets and asteroids might threaten our planet was not widely accepted until the 1980s. Then astronomers began to worry. Comet Swift-Tuttle is big, about the same size as the asteroid that wiped out dinosaurs 65 million years ago, and as recently as 1992 it seemed that Swift-Tuttle might strike Earth in the year 2126. New data and calculations show otherwise, though. There's no danger of a collision for at least a millennium and probably much longer.
So relax. Enjoy the show. Perseids are harmless ... and beautiful. This is an unusually good year to see for yourself